(a) Field of the Invention
The present invention relates to processing of an electrically conductive substrate in a method for the preparation of a selenium type electrophotographic element.
(b) Description of the Prior Art
Methods for preparing selenium type electrophotographic elements have hitherto been known which comprise the steps of turning or buffing the surface of an electrically conductive substrate which has a metal surface until its surface-roughness Rz (according to JIS-B0601) becomes 0.01 to 0.4 .mu.m (that is from 0.01 .mu.m or more to 0.4 .mu.m or less), then etching the same and thereafter vapordepositing thereon selenium, selenium alloy or selenium compound (which will be called "selenium type" for short hereinafter); or the steps of subjecting the surface of said substrate to super-finishing (a processing method using vibration and sliding of a grindstone) until its surface-roughness becomes 0.3 to 2.0 .mu.m and thereafter forming a selenium type-vapordeposit layer in the same manner as mentioned above. However, both methods include difficult points in the preparation. The former method is defective in the following points (1) the cost of equipment increases because an etching treatment is needed in addition to surface processing, (2) the characteristics of the elemenet such as external appearance, adhesive property and the like are not uniform because control of the etching liquid during the etching treatment is difficult and thus the pit state (surface-roughness) varies as the liquid concentration varies, (3) a part to be cut is required in processing for regeneration, and therefore the number of regenerations is about one at most and repeated regeneration is difficult, and (4) in case As.sub.2 Se.sub.3 is used in the vapordeposit layer, when conducting an etching treatment in processing for regeneration, a small amount of As.sub.2 Se.sub.3 adhering to the surface other than the regeneration-processed (or turned) surface dissolves in the treating liquid and generates gas which inflicts bodily injury on a person, whereby expensive equipment is required for treating this poisonous gas. On the other hand, the latter method is free from the drawbacks inherent in the etching treatment but is defective in that when As.sub.2 Se.sub.3 vapordeposit layer is superimposed on the surface of the substrate after processing, a large number of projections occur on the surface of the vapordeposit layer and injure the blade for toner cleaning when matching the obtained element with an electrophotographic copying machine, whereby the obtained copy deteriorates in quality. The number of projections generated depends on the degree of surface-roughness of the substrate. In case Rz is 0.3 to 2.0 .mu.m, the obtained element, even if the vapordeposit layer is processed, is not permissible from the aspect of its matchability with an electrophotographic copying machine.